As one of the lock releasing mechanisms as described above, there are those disclosed in Patent Document 1 (JP-A-7-208008) and Patent Document 2 (JP-A-2001-266). Strictly speaking, Patent Document 1 is a mechanism which is operated when locking the locking mechanism, but the description will be given assuming that the mechanism is used as an lock releasing mechanism. In Patent Document 1, a main switch, a motor configured to rotate by an current passing operation by the main switch, a conversion gear mechanism configured to convert the direction of rotation output of the motor, converting means configured to convert the rotating motion to the reciprocal swinging motion, a reciprocating member configured to reciprocally swings between a neutral position and a full-stroke position by the converting means, and a spring configured to urge the reciprocating member constantly to the neutral position are provided. The conversion gear mechanism includes a worm gear fixed to a rotating shaft of the motor and a substantially disk-shaped base gear configured to mesh the worm gear. The converting means includes an inertia plate configured to engage the base gear via the spring, a link gear configured to mesh a swing gear, and a clutch pin configured to interlock the link gear with the base gear. The inertia plate is disposed coaxially downwardly of the base gear. The link gear is disposed coaxially above the base gear.
Upon passage of a current the main switch, the base gear rotates via the worm gear of the motor. In conjunction with this, the inertia plate is also rotated by the spring. Accordingly, the clutch pin projects into a circumferential groove between the base gear and the link gear. Then, the clutch pin engages an engaging projection of the link gear, whereby the link gear is rotated. Upon the rotation of the link gear, the swing gear swings in the lateral direction, so that the coupling member coupled to the swing gear is towed to lock (unlock) the locking mechanism. A series of motions is achieved by a power source being supplied from the main switch to the motor for a sufficient predetermined period, and the limit of the swinging motion of the swing gear is defined by a stopper. When the motor is stopped, the inertia plate is restored to the neutral position by the spring which urges in the direction of reverse rotation. At this time, the clutch pin is stored in the base gear, and the engagement with the engaging projection is released. Accordingly, the interlocked relationship between the base gear and the link gear is released.
In Patent Document 2, a main switch configured to perform the current passing operation when releasing the locked state of the locking mechanism, an actuator having a drive shaft projecting and retracting upon current passage via the main switch, transmitting means configured to reciprocally swing between a neutral posture and a full-stroke posture upon receipt of an output from the actuator, an urging member configured to constantly urge the transmitting means to the neutral posture, and two limit switches which forcedly stop the actuator are provided. The transmitting means employed here includes an actuating arm configured to swing in association with the activation of the actuator, and a locking member configured to lock the swinging motion of the actuating arm.
When the actuator is actuated to project upon receipt of the operation of the main switch, the actuating arm swings to the full-stroke posture, so that the coupling member is towed and the locking mechanism is unlocked. When the actuating arm assumes the full-stroke posture, the locking member comes into abutment with a first limit switch. Accordingly, the actuator is forcedly stopped even though the main switch is continuously pushed. When the operation of the main switch is released, the actuator is operated to be retracted. In conjunction with this, the actuating arm is swung to restore the neutral posture, and the locking mechanism is brought again into the locked state. When the actuating arm assumes the neutral posture, the locking member comes into abutment with a second limit switch, so that the actuator is forcedly stopped.
In Patent Document 1, the main switch must be pushed continuously until the locked state of the locking mechanism is completely released, so that the operation of the locking mechanism is complicated. In other words, when the operation of the main switch is released in the course of the operation of the locking mechanism, the locked state of the locking mechanism cannot be released. In addition, in order to retain the swing gear at the full-stroke position, the main switch must be continuously pushed. The limit of the swinging motion of the swing gear is retained by the stopper. In this configuration, since the power source is continuously supplied to the motor while the swing gear is retained at the full-stroke position, an unnecessary load is applied to the motor, so that there is apprehension that the motor is subjected to damages or early deterioration. In contrast, in Patent Document 2, even when the main switch is continuously pushed, the actuator can be stopped forcedly by the first limit switch, so that the unnecessary load is not applied to the actuator. In a case of releasing the operation of the main switch and returning from the full-stroke posture to the neutral posture, the actuator is stopped by the second limit switch in the neutral posture. However, even in Patent Document 2, the main switch must be pushed continuously until the locked state is completely operated to the unlocked state, and in order to retain the locked state. In other words, when the operation of the main switch is released in the course of the operation of the locking mechanism, the locked state cannot be released. In the first place, bringing the reciprocating member into the reciprocating motion only by one-push operation such as to push the main switch once and release immediately is substantially impossible because the actuator (solenoid) configured so that the drive shaft is actuated in the retracting direction upon release of the operation of the main switch is employed. Suppose it is possible, increase in complexity of the mechanism is inevitable.
This specifically presents a problem in a locking mechanism which is required to continue the unlocked state to some extent. For instance, a case where the lock releasing mechanism is coupled to the locking mechanism of an electric reclining mechanism in a power seat for a vehicle is exemplified. A seatback of the power seat is configured to be electrically adjustable in reclining angle by operating a main switch disposed at an adequate position in the vehicle. Therefore, the unlocked state needs to be retained at least for the duration of the operation of the reclining angle of the power seat. However, with the lock releasing mechanism as disclosed in Patent Document 1 and Patent Document 2, the full-stroke position in which the coupling member is towed cannot be retained unless the main switch is continuously pushed. In this configuration, the operation to move the power seat from the fully reclined state to a basic posture, then to a folded state beyond the basic posture cannot be achieved only by the one-push operation such as to push the main switch once and release immediately.
Thus, there is a need in the art for a lock releasing mechanism in which an actuated state is continued for a predetermined period even after the current passing operation via the main switch is immediately released, and a full-stroke position in which a coupling member is towed can be retained.